Deaeration of viscous liquids



L. H. DE LANGEN DEAERA'I'ION OF vlscous LIQUIDS May 19, 1959 2 -Sheets-Sheet 1 Filed Oct. 15. 1954 y 1959 L. H. DE LANGEN DEAERATION OF vlscous LIQUIDS 2 Sheets-Sheet 2 INVENTOR Filed Oct. 15. 1954 DEAERATION F VISCOUS LIQUIDS Lambertus Hendrik de Langen, Arnhem, Netherlands, assignor to American Enka Corporation, Enka, N.C., a corporation of Delaware Application October 15, 1954, Serial No. 462,462 Claims priority, application Netherlands October 17, 1953 4 Claims. (Cl. 233-27) This invention relates to gas and liquid separation and more particularly to the removal of dissolved gases from substances such as viscose spinning solutions.

It has long been the practice to deaerate spinning solutions before they are extruded to form films, yarns, bands or the like. In the past filmlike bodies of the spinning solution have been subjected to long storage under negative pressure either with or without boiling but, regardless of the scheme used, the results have been disappointing. While the storage of a thin film of solution under sufiicient negative pressure to cause boiling will result in substantial deaeration, the foam formation is such as to counteract the effect of the deaeration. Furthermore, the known chemical and mechanical schemes for controlling foam are not, in this instance, effective.

It is therefore an object of the present invention to provide a fully effective way of removing gas from liquids and more particularly from viscous liquids such as viscose spinning solutions.

It is proposed according to the present invention continuously to deaerate spinning solutions by centrifuging the same under reduced pressure While completely avoiding residual foam.

Other objects and advantages of this invention will be apparent upon consideration of the following detailed description of a preferred embodiment thereof in conjunction with the annexed drawings wherein:

Figure 1 is a view in elevation of a complete degasification. system according to the present invention;

Figure 2 is a view in vertical section to a much enlarged scale the centrifuge of the system of Figure 1;

Figure 3 is a view in cross section taken on the line 3--3 of Figure 2;

Figure 4 is a view in cross section taken on the line 4-4 of Figure 2;

Figure 5 is a view in cross section taken on the line 5--5 of Figure 2; and

Figure 6 is a view in cross section taken on the line 6-6 of Figure 2.

Referring in detail first to Figure 1, the viscose to be treated enters the system at valve 10. It is then lifted through conduit 11, heat exchanger 12 and conduit 13 to the centrifuge 14. A vacuum is imposed on the centrifuge 14 by a pump 15 connected through a conduit 16. The deaerated spinning solution leaves the bottom of the centrifuge through a conduit 17 leading to a pump 18 which delivers the viscose to use through a conduit 19.

The heat exchanger 12 is supplied with a heating fluid through line 20 and this fluid is kept at a temperature such that the viscose delivered to the centrifuge is preheated to the most favorable temperature for deaeration.

The centrifuge 14 is driven by an electric motor 21, see Figure 2. The motor 21 is driven by a generator 22 connected through a positive infinitely variable drive 23 with a motor 24. Such drives are well known in the United States Patent 0 art as P.I.V. drives. The scheme shown. is a voltage control arrangement whereby, upon adjustment of the P.I. V. drive 23, the output of the generator 22 can be varied in turn to control the speed of the centrifuge motor 21. Any other suitable speed control arrangement for the motor 21 may be used.

The pump 15 is of the water jet type, the liquid being drawn from reservoir 25 by a pump 26 and delivered to: the jet pump 15 through a conduit 27. The liquid with the entrained gas from the conduit 16 is returned through pipe 28 to the reservoir 25. Line 29 is an overflow line for the reservoir 25.

The centrifuge of Figure 2 has a vertically disposed cylindrical housing divided into four sections 30, 31, 32 and 33, these sections being connected together by flanges for ease of assembly and access for repair. The motor 21 is housed in section 30 but is supported from section 31 by a short hollow standard 34 connected by a spider 35 to the wall of section 31. The motor 21 is connected through a clutch having discs 36 and 37 to a rotor 38 which is keyed at 39 to the clutch disc 37.

The rotor 38 is comprised of end shafts 40 and 41 and an intermediate hollow cylindrical portion 42 connected by radial webs 43 and 44 to the end shafts 40 and 41 respectively. The webs 43 and 44 are welded to the respective end shafts and to the cylindrical portion 42.

A bearing 45 is provided for the upper end shaft 40 of the rotor 38 and a bearing 46 is provided for the lower end shaft 41. Bearing 45 is sealed against loss of lubricant by a cap 47. The bearing 46 supports a measure of the weight on the rotor 38 and, to this end, the bearing is supported by four radial fins 48 which are in turn fastened as by welding to the casing section 33, see Figure 6. Horizontal discs 49, 50 and 51 are provided to strengthen the webs 43 and 44 respectively.

These discs extend radially for less than the full radius of the respective webs. a

The viscose or other liquid to be deaerated is delivered to the centrifuge 14 through the tube 13 which connects to a fitting 52. The fitting 52 leads to an annular tube 53 which is disposed in a horizontal plane concentrically above the cylinder 42. The tube 53 is provided with circumferentially spaced apertures 54 in its lower extremity and the liquid is delivered to the centrifuge through these apertures. An annular skirt 55 depends from the tube 53. The skirt 55 is concentric to the group of apertures 54 but is on a somewhat greater radius. Below the skirt is plate or disc 49 which is normal to the axis of rotation of the rotor 38 and of a diameter greater than the outside diameter of the skirt 55. The area of the centrifuge adjacent to the ring 53 is subject to observation through sight glass 56. Sight glasses or observation windows are also provided at 57 near the lower bearing 46 and at 58 below the fins 48.

Vacuum is applied to the system through fitting 59 which connects to line 16.

At the bottom of the rotor 38 there is a skirt 6t) and this skirt extends into an annular slot 61 in the horizontal top of an annular reservoir 62 of triangular cross section. The frusto conical wall 63 of the reservoir 62 rests upon the top of fins 48. Cylindrical Wall 64 of the reservoir 62 is provided with a plurality of circumferentially spaced apertures 65 which spill the contents of the reservoir.

The viscose is discharged from the tube 53 as an annular curtain or body. The tube 53 and skirt 55 are, of course, stationary being supported from the fitting 52. The annular body of liquid begins to move however as it strikes the disc 49 which, as a part of the rotor 38, is

rotating. The liquid is thrown out by the disc 49 against.

the inner wall of the rotating cylinder 42. The liquid held against the inner wall of the cylinder 42 by centrifugal force and fiows down that wall by gravity to be received in the reservoir 62. A pool is built up in the reservoir 62 to the level ofthe apertures 65. After leaving the reservoir 62 the liquid flows first as an annular body and finally as a cylindrical body in the long section, see Figure 1. The bottom of the skirt 60 is spaced a few millimeters above the plane of the apertures 65 so that, during operation, a short cohesive liquid screen is formed between the quiet pool of liquid in the reservoir 62 and the bottom of the skirt 60. The advantage'of this spacial relationship is to prevent spraying of the liquid leaving the centrifuge which, if per mitted, is a major source of foam'formation. Liquid from the reservoir 62 discharges through aperture 65 under low velocity conditions which avoids splash and the formation of foam. 7

Apparatus depicted in Figure 1 is to approximate scale and the vertical distance from the planeA in which the pump 15 is located to the plane'B which is about midway of the centrifuge is 204 centimeters. This being the case, the height of the column 66 is greater than the height of the maximum column of deaerated material which atmospheric pressure can support. Actually so long as the length of the column below the bottom of the centrifuge 14 is in excess of meters, a barometrically active column of viscose spinning liquid isformed. The effect of the barometric column is to assist in maintainmg the vacuum within the'centrifuge and the parabolic liquid surface in the container 66 will always be kept at the required distance below the centrifuge. At any load of the apparatus, the discharged amount of the deaerated liquid will adjust automatically to the supply.

The thinness of the film formed onthe cylinder 42 is importantly related to the quality of the degasification. It is apparent that the film thickness is a function of the rate of supply of the liquid and the acceleration of gravity. It is likewise related to viscosity, and, where the liquids are very viscous, it is desirable to assist the effect of gravity by making the cylinder 42 in the form of the frustum of a cone. If this is done the cone is on a vertical axis with the wider portion down. In this way the increasing diameter as the liquid flows down Wardly results in an increasing centrifugal force aiding gravity to maintain a satisfactorily thin film on the inside of the centrifuge. In general, a conicity' of from l-6 will be satisfactory depending,of course, upon the viscosity of the materialdealt 'with, the speeds used and the throughput per unit timeg; I

By the use of the present invention it is possible to reduce the totalair content down to something between .4 and .1% by volume as compared to viscose under atmospheric pressure and'at room temperature which normally'contains about 1% by volume of dissolved air.

In order to insure smooth 'runnin'g'of the centrifuge particularly if the diameter is several decimeters or greater and the length is several meters or more, the rotor is prebala'nced before use. Speeds up to 1800 rpm. are contemplated.

The spinning liquid to be treated'may be preheated in heat exchanger 12. The starting liquid will be prefilteredfby conventional means not shown. The walls of the centrifuge, particularly the "cylindrical inner wall of thefpart 4-2, should be provided with a smooth resistant lining which is difiicult to wet. In the case of viscose a special artificial resin consisting of a condensation product of epichlorohydrin and bisphenol is very suitable for this purpose.

What is claimed is:

1. The method of degasifying viscose that comprises forming and maintaining a thin film of annular section of the viscose to be degasified, rotating the film at high speed under reduced pressure, gravitating the film in the form of a continuous curtain into an annular pool and spilling the contents of the pool under low velocity conditions into a column of a height greater than can be maintained by atmospheric pressure with material of the specific gravity of the liquid undergoing degasification.

2. Degasification apparatus comprising a housing, means to evacuate said housing, a hollow body of annular cross section vertically mounted in said housing for rotation about its axis, means to rotate said body, means for supplying an annular curtain of viscous liquid to be degasified through the upper end of said body, a horizontally disposed disc mounted within said body and adapted to throw said liquid against the inner surface of said body near its upper end, walls defining an annular reservoir having a mouth in adjacent coaxial registry with the bottom of said body, said reservoir having spill apertures in the walls which lie radially outwardly of its mouth andmeans to remove said liquid at the bottom of said housing.

3. Degasification apparatus comprising a housing, means to evacuate said housing, a hollow body of annular cross section vertically mounted in said housing for rotation about its axis, means to rotate said body, means to supply a viscous liquid to be degasified through the upper end of said body, a horizontally disposed disc mounted within said body and adapted to throw said liquid against the inner surface of said body near its upper end, walls defining an annular reservoir having a mouth in adjacent coaxial registry with the bottom of said body, said reservoir having spill apertures in the walls which lie radially outwardly of its mouth, a column attached to the bottom end of said housing and positioned below said apertures for receiving said liquid to a height greater than can be maintained by atmospheric pressure and means to remove said liquid from said column.

4. Degasification apparatus comprising a housing, means to evacuate said housing, a hollow body of annular cross section vertically mounted in the upper end of said housing for rotation about its axis, means to rotate said body, means for supplying an annular curtain of viscous liquid to be degasifi ed through the upper end of said body, means in said body for throwing said liquid against the inner surface of said body near its upper end, Walls defining an annular reservoir having a mouth in adja cent coaxial registry with the bottom of said body, said reservoir having spill apertures in the walls which lie radially outwardly of its mouth, a column attached to the bottom end of said housing and positioned below said apertures for receiving said liquid at a height greater than can be maintained by atmospheric pressure and means to remove said liquid from said column.

References Cited in the file of this patent UNITED STATES PATENTS 1,529,884 Ha 11 Mar. 17, 1925 1,634,245 Jones et a1. June 28, 1927 2,228,816 Doran Jan. 14, 1941 2,592,680 Goodwin Apr. 15, 1952 2,634,907 Smith Apr. 14, 1953 2,737,857 Lee Mar. 13, 1956 

